After watching the nice help videos for the Entourage eDGe, I noticed that there were two features which I don't think were covered by the tutorials -- and I wondered if anyone could tell me more about them.

(1) There's a WiFi switch on the "top" edge of the eDGe between the SD card slot and the PC USB input. When my eDGe is on and I move it to the "off" position, a little airplane silhouette appears in the top menu bar. Airport mode? What does the switch do and how is it effectively used?

(2) And then, right next to the SD card slot is a SIM card slot. What is that -- or more importantly -- how would an Entourage eDGe user make the best use of it?